I have no problem with the ancestry of my fellow countrymen. I have known many people from all over the world in my life, who have chosen to become Americans. I see little more upon which to comment.
Right now, I work with a few who are first generation, naturalised Americans ... a man from UAE, a man from Zimbabwe, a woman from India, two young brothers from Pakistan, a Samoan man, a Haitian woman, a young girl from Albania and a man from the Dominican Republic (although he is still using a work permit). Our store's employee roster is about one hundred ten these days. Several religions are also represented.
A brief list of real people I know or have known personally, with enough German in them to still carry Germanic surnames (although some of their names have been anglicised):
Zook, Snell, Boelsterbaum, Schaefer, Yoder, Baer, Betts, Culp, Cramer, Faulks, Shnavely, Jungblut, Hostetler, Sauter, Gaitz, Kistler, Caine, Boehmer, Lang, Rister, Mueller, Myer, Nuemann, Bogir, Pfeifer, Roth, Reinhardt, Klein, Schultz, Ault, Bauman, Bowman, Von Braun, Gerber, Kleibermann, Zimmerman, Brubaker, Boecher, Freuhoff, Gunther, Kapstein, Vogel, Hofner, Heissman, Weiand, Shlegel, Kester, Dreyer, Mohr ... and I'm sure I can think of many more, given time.
That represents just the people I now know, have worked around in the past or are related to me, who are obviously of German heritage.
I don't really think I see your point.
Why does it seem odd to you that a mass of people would leave a certain country, then have to go to war with that country?